| Mercury (Hg) is a global pollutant with neurological toxicity. Mercury spreads into water by many different processes including wet and dry deposition, input and surface runoff, resuspension and diffusion from sediment. Mercury, in the reservoir, proceed physical, chemical and biological transport and transformation processes. The activity of mercury in water body of reservoir will be increased as well as the enrichment of animal and plant. Mercury also has a significant influence on eco-environment in reservoir.Because of long-term alternating of dry and wet process, the environmental characteristics and existence of mercury would be changed, which affect the migration and transformation of mercury, then enhance the ecological damage of mercury in reservoir. Therefore, it is important for us to study the temporal and spatial variation of mercury in water bodies of typical riparian zone in three Gorges. And it is meaningful to understand the mercury distribution characteristics and affecting factors of mercury in water bodies of typical riparian zone in three Gorges. What’s more, establishing database of various forms of mercury in the water body of typical riparian zone in three Gorges is significant.In order to find out the spatial and temporal distribution of the different species of mercury in the waterbody of typical water-level-fluctuating zone (WLFZ) in the TGR, hierarchical water samples in four typical WLFZ sites (Hanfeng Lake of Kai County,Zhenxi Fuling District,Shibaozhai Zhong County, Tujing of Zhong County) were collected according to water level from July2011to June2012. Total and dissolved mercury (THg, DHg) were measured by Cold Vapor Atomic Fluorescence Spectrometry (CVAFS) after oxidation, reduction and trap. Samples for total and dissolved methylmercury (MMHg, DMMHg) determinations went through distillation, ethylation and gas chromatographic (GC) separation before CVAFS analyses. Particulate mercury (PHg) and methylmercury (PMMHg) were obtained by subtrcting DHg from THg and DMMHg from TMMHg.Some main conclusions were obtained as follows:(1) The concentrations of THg were1.71-39.94ng/L, the average was14.25±9.01ng/L; The concentrations DHg were0.51-24.42ng/L, the average was6.68±4.93ng/L.The concentrations PHg were0.13-29.18ng/L, the average was6.96±7.11ng/L; The concentrations reactive mercury (RHg) were0.03-0.98ng/L, the average was0.33±0.27ng/L; The range of TMMHg was0.01-0.99ng/L, the mean concentration was0.23±0.20ng/L; The range of DMMHg was0.01-0.84ng/L, the mean concentration was0.14±0.14ng/L; The range of PMMHG was0.00-0.80ng/L, the mean concentration was0.09±0.11ng/L.(2) The different species of mercury in the water had spatial characteristics. The mean concentrations of THg decreased in order of Zhenxi Fuling District>Shibaozhai Zhong County>Han Feng Lake of Kai County>Tujing of Zhong County; the mean highest concentration of DHg was appeared in the water of Zhenxi of Fuling District, and the lowest was discovered in the Han Feng Lake of Kai County; the mean concentration of PHg in Zhenxi of Fuling District was higher than that in Hanfeng Lake of Kai County, Tujing of Zhong County, Shibao zhai of Zhong County; the mean concentrations of RHg decreased in order of Hanfeng Lake of Kai County>Tujing of Zhong County>Zhenxi of Fuling Distract>Shibaozhai of Zhong County. The mean concentrations of TMMHg, DMMHg, PMMHg were all decreased in order of Hangfeng Lake of Kai County>Tujing of Zhong County>Zhenxi of Fuling Distract>Shibaozhai of Zhong County. The mean concentrations of THg, DHg, PHg in main stream were all higher than those in the tributaries, the mean concentrations of RHg,TMMHg, DMMHg, PMMHg in main stream water were all lower than those in the tributaries.(3) The concentration of THg in the waterbody of Han Feng Lake was not merely significantly correlated to the concentration of DHg, but also significantly correlated to the concentration of PHg. And the correlation between THg and DHg was higher than that between THg and PHg. The concentrations of THg in the waterbody of Tujing Zhong County. Shibaozhai Zhong County and Zhenxi Fuling Distrct were all obviously correlated to the concentration of DHg, as well as PHg. The correlation between THg and PHg was higher than that between THg and DHg The concentrations of TMMHg in the waterbody of the four WLFZ were correlated to the concentration of DHg, as well as the PHg. The correlation between TMMHg and PMMHg was higher than that between TMMHg and DMMHg in Hanfeng Lake Kai County. And the correlation between TMMHg and DMMHg was better than that between TMMHg and PMMHg in another three water-level-fluctuating zones. The concentration of THg in the main stream and the tributaries were all correlated to the concentration of DHg, as well as the PHg. And the correlation between THg and PHg were better than that THg between DHg, obtaining from the main stream and the tributaries. Also the concentration of PHg in the main stream and the tributaries were correlated to the concentration of TSS remarkably. But various forms of mercury in the main stream and the tributaries had no significant correlation with DOC.(4) During the study period, the concentrations of different forms of mercury in the waterbody of WLFZ in the TGR changed with the water level fluctuation. The concentrations of THg in waterbody of four typical fluctuating zones were highest at the water level of145-160m and170-175m, and the lowest THg concentrations were discovered at the water level of160-170m. The concentrations of DHg were highest at the water level of145-160m, which were lowest at the water level of160-170m. The concentrations of RHg were highest at water level of170-175m, which were lowest at water level of160-170m and145-160m. All the concentrations of TMMHg, DMMHg, PMMHg decreased with rising water level, then increased with dropping water level. The concentrations of PHg in the waterbody of Tujing Zhong County, Shibaozhai Zhong County and Zhenxi Fuling District were highest at the water level of145-160m, which were lowest at the water level of160-170m. Meanwhile, the concentration of PHg in the waterbody of Hanfeng Lake in Kai County increased with rising water level, and decreased with dropping water level.(5) THg, DHg, PHg, RHg, TMMHg, DMMHg, PMMHg concentration in inshore and river have differences in the WLFZ of the TGR area, which change with the water level. Meanwhile, THg、DHg、PHg、RHg、TMMHg、DMMHg and PMMHg concentrations are different in different water layer, also changing with the water level. |
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